In general silver halide photographic materials, a color reproduction process by subtractive color process is employed, and in order to reproduce blue, red and yellow, this process utilizes coloring dye images of yellow, magenta and cyan which are the corresponding complementary colors, respectively.
Among them, the cyan dye image is produced by a cyan dye which is formed by coupling an oxidized product of an aromatic primary amine developing agent contained in a developer with a cyan dye-forming compound (hereinafter called a cyan coupler). Hitherto, phenols or naphthols have been used as cyan couplers.
The color images obtained from these cyan couplers, however, have several problems with respect to stability.
For example, a color image obtained from 2-acylaminophenolic cyan coupler which is described in specifications of U.S. Pat. Nos. 2,367,531 and 2,423,730 is generally inferior in fastness to heat, a color image obtained from 2,5-diacylaminol cyan coupler which is described in specifications of U.S. Pat. Nos. 2,369,929 and 2,772,162 is generally inferior in fastness to light, and 1-hydroxy-2-naphthamide cyan coupler is generally insufficient in fastness to both light and heat.
Couplers which have improved on these points include phenolic cyan couplers having an ureido group at the 2-position which are described in specifications of U.S. Pat. Nos. 3,446,622, 3,996,253, 3,658,308 and 3,880,661 and Japanese Patent Application (OPI) No. 65134/81 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"). In comparison with other general cyan couplers mentioned above, these couplers are much improved with respect to their fastness to light and heat.
However, for the reasons described below, the phenolic cyan couplers having ureido groups have serious defects in which the coupling with an oxidized product of a developing agent formed in a developer proceeds slowly. Accordingly, the sensitivity is lower than high-speed reactive cyan couplers as described in Japanese Patent Application (OPI) No. 1938/81, and disappearance of granularity becomes difficult to obtain, and so-called aggravation of granularity occurring with coloring of all the coated couplers, is also caused.
The reasons include (i) the dissociation equilibrium constant of the coupler is high, and in development, the concentration of the dissociated anion species which are active species of coupling reaction is low; (ii) as a bulky ureido group is situated at the ortho position adjacent to the coupling position, the steric hindrance becomes large, preventing the approach of the oxidized product of a developing agent.
Therefore, when attempting to use these couplers for photographing materials which require especially high sensitivity, they were insufficient in sensitivity. In order to fulfill the requirements relating to sensitivity, an increase in the amount of silver was required or silver halide grains having a large size were used which was accompanied by aggravation of granularity.